1. Field of the Invention
This invention relates to displaying subtitles in connection with a motion picture and more specifically to the use of a shutter that is synchronized to the projection of the subtitles to enhance the cinematic presentation.
2. Description of the Related Art
Motion pictures are filmed in many different languages, oftentimes more than one language in a given film, and distributed throughout a worldwide market. During the screening of such motion pictures there is frequently the need to display subtitles along with the moving images. The subtitles contain a translation of the motion picture sound track into the native language of the audience, and must be synchronized with the sound track and images.
Generally, the subtitles are imprinted on successive frames of the film print. The subtitles are projected onto the screen along with the images and are inherently synchronized with the sound track and the images. Imprinting is particularly time-consuming and extremely expensive. In addition, dedicating a given film to a particular language greatly reduces the flexibility in distribution.
To overcome these limitations, the motion picture industry is moving toward adoption of a dual-projector system of the type generically shown in FIG. 1 in which a primary projector 2 such as a standard film projector or a digital cinema projector projects a motion picture onto a display surface 4 such as a conventional movie screen. Subtitles are projected from a supplemental projector 6 onto a desired area 8 of the movie screen. The subtitle information is provided to the supplemental projector from a controller 10 that stores the subtitles, preferably in a digital format, in a storage medium 12. In response to a SYNC signal over line 14 from the projector, the controller 10 provides whatever subtitle is currently desired to the supplemental projector 6 for projection onto the screen 4. The SYNC signal maintains synchronism between the primary and supplemental projectors so that the appropriate subtitles are superimposed on the motion picture display at the correct times. Different techniques for synchronizing the subtitles to the motion picture are well known in the art. Specific implementations of a dual-projector subtitling system are described in European Patent Application EP 0 690 335 A1 and U.S. Pat. No. 6,046,778. U.S. Pat. No. 5,959,717 describes a dual-projector system, which is similar to the subtitling systems, but is used to add special effects and provide anti-piracy protection
Since the subtitles are stored separately from the film print, a non-subtitled print can be projected from the primary projector 2 and any desired subtitles added via the supplemental projector 6. The subtitles can be changed for the same print simply by replacing the storage medium 12 with a new storage medium having a different set of subtitles. Thus, any number of different subtitle sets can be used with the same film print, or no subtitles at all, without having to modify the print or provide a different print for each different subtitle set.
The present invention provides a motion picture subtitle system that enhances the cinematic experience by reducing visual artifacts associated with current subtitling systems. Typical artifacts include a faint milky white rectangle when the subtitles are in their xe2x80x9coffxe2x80x9d state due to the imperfect dark state of the subtitle projector, a fluctuation in the brightness and color balance when the subtitles first transition to their xe2x80x9conxe2x80x9d state, and an imbalance between the subtitle and scene brightness levels.
These artifacts are eliminated by inserting a shutter such as a mechanical dowser, LCLV, electro-optic (E/o) absorber or E/O diffuser in the optical path between the supplemental projector and the motion picture screen and synchronizing the shutter""s operation to the projection of the subtitles. The supplemental projector is separate from the primary projector and arranged to modulate a light beam during the xe2x80x9conxe2x80x9d state to superimpose subtitles on the motion picture. The shutter is positioned in the optical path of the supplemental projector to pass the light beam during the xe2x80x9conxe2x80x9d state and to substantially attenuate the light beam during xe2x80x9coffxe2x80x9d states. A controller is arranged to receive the subtitles from a storage medium, to provide the subtitles to the supplemental projector in synchronism with the projection of the motion picture, and to alternately cause the shutter to pass the modulated light beam during xe2x80x9conxe2x80x9d states in synchronism with the motion picture so the subtitles are superimposed at desired times on desired portions of the motion picture and cause the shutter to attenuate the light beam during xe2x80x9coffxe2x80x9d states.
During the xe2x80x9coffxe2x80x9d state the shutter blocks, absorbs or widely scatters any light from the supplementary projector depending upon the particular shutter configuration thereby eliminating the undesirable milky white rectangle artifact. The shutter itself is preferably not limited to on/off (pass/attenuate) states but is rather characterized by variable transmission between the two extremes. Accordingly, to eliminate the transient fluctuations associated with the subtitle""s transition to the xe2x80x9conxe2x80x9d state, the transmission of the shutter is preferably ramped from its attenuation state to its pass state. The variable transmission property is also used to adjust the subtitle brightness in accordance with the scene brightness of the motion picture.
In one particular embodiment, the shutter is an electro-optical diffuser made of a polymer dispersed liquid crystal (PDLC) material. In the xe2x80x9coffxe2x80x9d state, the PDLC droplets are randomly aligned so that their refractive index does not match that of the polymer in which they are dispersed. The material appears translucent and causes the light to scatter. When an electric field is applied across the material, the PDLC droplets reorient so that their refractive index matches that of the polymer. The material is rendered substantially transparent and passes the light with very low loss and minimal scattering in this xe2x80x9conxe2x80x9d state. The material""s transmission properties can be continuously varied across the entire surface by adjusting the applied electric field.
These and other features and advantages of the invention will be apparent to those skilled in the art, from the following detailed description of preferred embodiments, taken together with the accompanying drawings, in which: